1. The Field of the Invention
The present invention relates to apparatus and methods for an improved type of surgical laser device. In particular, the preferred embodiment of the invention relates to apparatus and methods for a surgically designed, carbon dioxide laser probe which provides a laser light emission that is polarized in a circumferential relation about the distal treatment end of the surgical laser probe. This circumferential emission of laser light results in up to about a 90% efficient use of light energy emitted from a carbon dioxide laser light generator.
2. The Background Art
The three types of lasers in common surgical use are the carbon dioxide, argon and Nd:YAG (neodymium-doped yttrium-aluminum-garnet) laser, each named after the lasing medium employed. The carbon dioxide laser has a wavelength of 10.6 microns and its light is invisible. This type of laser is absorbed by water. Since cells contain a high percentage of water, this laser is effective in tissue ablation because of rapid cell vaporization in a fine line.
The argon laser has a wavelength of 0.44-0.52 microns and its light is blue-green. This type of laser is absorbed by red surfaces including a thin layer of bright red blood, and is effective for coagulating small blood vessels or ablating superficial vascular lesions. This laser can be focused onto the end of, and transmitted via, a quartz fiber encased in a protective Teflon or polyethylene catheter. There is space around the quartz fiber through which gas or liquid can be directed at a target site. The laser exits the tip of the catheter with a conical distribution and a divergence angle of 7.degree.-20.degree..
The Nd:YAG laser has a wavelength in the near-infrared range and is therefore invisible. This type of laser is not as well absorbed as is the argon laser, and therefore penetrates three to five times more deeply into tissue. Because of this deeper penetration, a larger volume of tissue is heated, and therefore more power is required to raise the tissue temperature to adequately heat and coagulate protein. The deeper penetration of the Nd:YAG laser makes it very effective hemostatically, but it can also result in deeper injury to underlying tissue.
The pathologic conditions amenable to treatment by these conventional lasers are diverse, but include urethral stricture disease. Obliteration of the adenomous tissues common to the pathologic conditions is accomplished through thermal coagulation by use of the Nd:YAG and argon ion lasers. Argon-pumped dye lasers are capable of treating adenomous tissues by destroying the cells of the tissue through cytotoxic photochemical reactions generated in the presence of a photosensitizer, such as hematoporphyrin derivative. The power output of the latter type of laser is insufficient to thermally destroy adenomous tissue under treatment.
Intravesicle chemotherapy, i.e., repeatedly instilling cytotoxic chemotherapeutic agents into a diseased area constitutes a second-line mode of therapy when resection fails to control recurrences of adenomous tissues. The latter form of therapy controls recurrences in approximately twenty-five to 45% of the cases, but involves multiple catheterizations, extending over a period of up to two years, with weekly catheterizations required during the first six weeks of therapy.
In the treatment of diseased areas characterized by the presence of adenomous tissue, recurrent modes of laser treatment by conventional techniques have proven ineffective for the elimination of recurrence of the disease after treatment, as compared with other forms of conventional therapy of the type described above. The Nd:YAG laser is suitable for treating selected patients with urethral stricture disease as outpatients, but may not be cost effective primarily due to the high cost of the laser system required. Argon pumped dye lasers require the presence of a photosensitizer to generate a cytotoxic photochemical reaction in order to destroy cells of adenomous tissue. A potential advantage of this form of surgery is that the cells of the tissue will be destroyed selectively because of the preferential absorption and/or retention of the photosensitizer by the cells of the adenomous tissue.
To date, it appears that well differentiated adenomous tissue areas respond poorly to the latter form of therapy. Also, hematoporphyrin derivative, the most widely used photosensitizer, is retained by the skin for approximately two to four weeks and thus require a patient to avoid direct sunlight for at least a four-week period of time. Retreatments, if frequent, become vexing to a patient.
The carbon dioxide laser overcomes many of the shortcomings of the other types of above-discussed lasers. For example, the carbon dioxide laser enables laser ablated areas to heal with a minimal amount of scar formation, does not require a photosensitizer to effect its cytodestructive effects, and is substantially less expensive than the Nd:YAG or argon ion laser systems of equivalent power output.
The use of carbon dioxide lasers, however, involves focusing a large amount of incident laser energy directly onto one point. Any laser energy not focused is randomly discarded to the surrounding environment as by-products in the form of heat and light. Because the concentration of a large amount of laser energy from carbon dioxide lasers has not been accomplished, much of the laser energy from carbon dioxide lasers is lost, and their efficiency minimized. It has been that use of carbon dioxide lasers results in a 100% power emission from which one is able to only use about 3% to 15% of the power generated by the laser. Thus, although the use of carbon dioxide lasers could be effective for the transurethral resection of adenomous tissues in urethral stricture diseases, such use of prior carbon dioxide lasers would be inefficient in terms of net power available for certain surgical procedures.
Additional shortcomings associated with the surgical laser prior art include inadequate stearability of laser light during surgical procedures. This point is emphasized during the transurethral resection of benign prostatic hypertrophy in a patient where all of the adenomous tissue cannot be adequately reached. It may be difficult for a surgeon to maneuver the handle of a laser probe in a narrow channel such that laser light is directed to a specific target. Moreover, surgeons have complained that any movement of laser devices during the transurethral resection of benign prostatic hypertrophy could cause damage to the prostatic sphincter muscles.
Some attempts have been made in the art to provide for angled laser light such that movement in the urethral canal is minimized. Such angled laser light has been demonstrated by the use of a lens to focus laser light to a point in a plane at right angles to the longitudinal axis of the laser device. This type of angled laser light, however, has not been entirely satisfactory in all situations.
Although in the angled configuration laser light is directed in a plane away from the plane normally followed by the laser device, the laser light is merely directed in another area. Therefore, if a number of areas are to be exposed to the laser light, the laser device must be manipulated in a rotational fashion so that the laser light can be directed at the various target sites. Such a procedure is not only time-consuming, but involves a risk to a patient due to the large amount of movement of a surgical tool within a patient's body.
In light of the foregoing, it is clear that many problems presented in the laser device area have not been solved. There is a need for a laser device which could solve these additional problems not remedied by currently known laser devices.